Dummy bar for continuously casting metals



Feb. 28, 1967 c. w. SAUNDERS DUMMY BAR FOR CONTINUOUSLY CASTING METALS 2 Sheets-Sheet 1 Filed July 6, 1964 Feb. 28, 1967 c. w. SAUNDERS DUMMY BAR FOR CONTINUOUSLY CASTING METALS 2 Sheets-Sheet 2 Filed July 6. 1964 United States Patent 3,305,899 DUMMY BAR FOR CONTINUOUSLY CASTING METALS Charles W. Saunders, Aspatria, Cumberland, England, assignor to The United Steel Companies Limited, Yorkshire, England, a British company Filed July 6, 1964, Ser. No. 380,431 Claims priority, application Great Britain, July 10, 1963, 27,346/ 63 7 Claims. (Cl. 2257.2)

In the continuous casting of metal such as steel the liquid metal is poured into an open-ended mould. At the beginning of each cast-it is necessary to use a dummy bar, that is to say a bar with a head which fits the mould and holds the liquid metal in the mould during initial solidification, this bar then being drawn downwards through rolls. The usual dummy bar is straight and rigid, and when it has passed through the rolls it is detached from the head, usually through some form of quickrelease coupling, and vertically dropped into a pit, which is about 20 feet deep.

This practice requires hoisting mechanism for raising the dummy bar from the pit and feeding it upwards into the bottom of the mould, mechanism for detaching the dummy bar to drop it into the pit and the excavation of the pit. It also contributes materially to the overall height of the continuous casting machine, which is one of the chief drawbacks of conventional machines.

In some continuous casting machines the strand, after the dummy bar has been detached, is bent to a curve so that it can pass horizontally through a straightening machine, from which it emerges in a horizontal direction and is then cut into convenient lengths.

In machines recently developed the mould is itself curved so that the strand is curved at all times, and passes through a roller track having the same radius of curvature which acts essentially as a guide in leading the strand to a straightening machine, from which it emerges horizontally to be cut. Such casting machines are of much less overall heights than the previous machines, and for use in them a flexible dummy bar is essential. Such a dummy bar must be capable of being fed upwards between all the rolls which engage the opposite sides of the strand during withdrawal until it reaches the bottom of the mould. In operation the bar can then be Withdrawn along the same track, followed by the strand. On reaching the straightening rolls, the dummy bar is horizontal, and thus easily disposed of during the casting operation by moving it to one side or the other, or dropping it below the straightening machine. A dummy bar capable of use in this way, however, must be flexible enough to follow the curved track while at the same time being able to withstand the compressive load to which it is subject while being pushed upwards into position.

Flexible dummy bars are known. Some such bars are made of rubber, but these lack durability, and in particular cannot withstand the high compressive forces to which they are subjected on passage through withdrawal rolls. Other flexible bars are composed of steel chains, but these have not enough rigidity to resist the axial compressive loads to which they are subjected, and their lack of rigidity is disadvantageous at the discharge end of the machine.

According to this invention a flexible dummy bar consists of a link chain having one or more resilient rods threaded through the mad the chain and restrained against lateral movement at the pivot points but between these free to bend, so that each rod may assume a regu lar arc as the chain runs round a curve. The rod or rods give the chain lateral stability under a compressive load.

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Most conveniently the chain links are outer and inner plates connected by pivot pins and spaced apart to leave gaps for the reception of the rod or rods. These gaps may conveniently be formed by spacers carried by each pivot pin between plates pivoted on it.

In order to restrain each rod laterally at each pivot pin a dowel pin may be inserted in a hole in a plate to extend into a gap in which the rod lies, the rod passing between the pivot pin and dowel pin.

The dummy bar must, of course, have a head as usual, and this head must be of the proper size to fit the mould. It is not necessary that the bar itself should be of the same cross-sectional size as the head, though the links should be of the same width as the strand so that they will engage the opposite rollers in the roller path in just the same way as the strand does. It is, however, convenient if the width of the chain, that is to say the axial length of the pivot pins, is equal to the second cross-sectional dimension of the strand, since then the dummy bar is best able to resist the various tensile and compressive forces to which it is subjected. Although in its simplest form the dummy bar may c0n sist of only two sets of links with the rod or rods between them, it is preferred always to provide more sets of links than these. In its preferred form the chain is composed of two or more pairs of outer and inner links with pivot pins common to all the links, and two rods, one on each side of each pivot pin, between the outer and inner links of each pair.

The invention will now be described in greater detail with reference to the accompanying drawings, in which:

FIGURE 1 is a side view of part of a simple form of dummy bar;

FIGURE 2 is a section on the line IL-II in FIG- URE 1;

FIGURE 3 is a side view of the head end of the preferred form of dummy bar;

FIGURE 4 is a plan of the part of the dummy bar shown in FIGURE 3;

FIGURE 5 is a section on the line V-V in FIG- URE 3;

FIGURE 6 is a diagrammatic elevation of a machine in which a flexible dummy bar is used; and

FIGURE 7 is a fragmentary plan of part of the machine shown in FIGURE 6 and is on a larger scale.

The dummy bar shown in FIGURES 1 and 2 is of a simple type, in that the chain is composed of three sets of links, namely two sets .of outer links 1 and 2 and a single set of inner links 3, all the links consisting of rectangular steel plates. The links are joined by pivot pins 4, each of which is surrounded by two circular spacers 5 and 6 lying one on each side of the inner link 3. Four steel rods 7 are threaded through the length of the chain, two of them in the gaps formed by the spacers 5 between the outer links 1 and the inner links 3, and the other two in the gap formed by the spacers 6 between the outer links 2 and the inner links 3. These rods pass outside the spacers and are restrained laterally by dowel pins 8 which pass through holes in the inner links 3. The rods 7 may be of spring steel and, for example, A-inch in diameter. The spacing between the pivot pins 4 may be, for example, 6 inches. The width of each link may then be 3 inches, thus rendering the chain suitable as a dummy bar in the casting of strands having one dimension of 3 inches.

The head of the dummy bar formed by this chain is not shown.

The dummy bar shown in FIGURES 3 to 5 is suitable for use in the casting of strands 5 inches square in section. It is composed of four sets of links, namely inner links 10 and 11 and outer links 12 and 13, with pivot pins 14 others in the gap between the other set.

common to all the links. Each pivot pin 14 is surrounded by a bush 15 between the links 10 and 11 and by two spacers 16 and 17. There are four rods 18, two in the gap between one set of inner and outer links and the Dowel pins 19 pass through both the inner links 10 and 11 adjacent to each pivot pin.

The leading end of the dummy bar comprises a U- shaped member 20 which is pivotally connected to the last pair of inner links of the chain and an end plate 21. The member 20 is bored to receive a stem 22 integral with the end plate 21, and a transverse pin 23 passes through the member 20 and a hole in the stem 22 to hold the end plate on the member 20. The end plate is tapped to receive a threaded pin 24 having collars 25 which act as keys for the cast metal. A steel chill plate 26 and an asbestos gasket 27 surround the pin 24, the asbestos insulating the member 20 from the chill plate 26 and from the molten metal that solidifies on the chill plate.

FIGURES 6 and 7 show diagrammatically a plant in which the flexible dummy bars may be used. This comprises a curved mould 30, a secondary coo-ling Zone 31 including rollers 32 by which the strand is guided, a curved withdrawal track formed by rollers 33, a straightening machine 34 including positively driven withdrawal rolls 35, and a horizontal roller track 36. The machine is shown in FIGURE 6 in the operation of casting a strand 37. FIGURE 7 shows a dummy bar 38 parallel to the strand and ready for use in the next cast. This dummy bar 38 rests in channel-shaped supports 39, each connected to the plunger 40 of a pneumatic ram 41. When a cast is to begin, the rams 41 are operated sothat the supports 39 are moved, carrying the dummy bar with them. The dummy bar is thus brought into position above the horizontal track 36, and can be pushed between the withdrawal rolls 35, which are then driven in the reverse direction to force the dummy bar up the track until its head enters the bottom of the mould and close it. When metal enters the mould it meets the head of the dummy bar and the bar and strand are then withdrawn by the rolls 35. A burner 42, carried by a trolley 43 which travels at the same speed as the strand, cuts through the strand at a little distance, say 2 feet, from the head, and immediately thereafter the dummy bar is engaged and moved laterally by the pneumatic ram 41 back to the position shown in FIGURE 7. When it is in this position the metal attached to the head is stripped and a fresh chill plate and pin are fixed to it ready for the neXt cast.

The rods need not be continuous. If the rods are to be inserted after the chains have been assembled, it is necessary to straighten the chain and pass the rods through the openings between the pivot and restraining pins, and it is more convenient to do this if the rods are shorter than the chain. The junctions between individual rods in difierent lengths of rods may advantageously be staggered.

Although the flexible dummy bar according to the invention is particularly useful in machines in which the strand is curved, the rigidity imparted by the rods is adequate to allow it to be used in any conventional machine and in machines in which the withdrawal track is of parabolic or other shape.

I claim:

1. A dummy bar for use in the continuous casting of metal comprising a chill plate and a link chain including pivoted links, at least one resilient rod extending through the run of the chain, and means restraining the rod against lateral movement only at the pivot points of the chain so that the rod is free to bend between the pivot points and the rod may assume a regular are as the chain runs round a curve.

2. A dummy bar according to claim 1 in which the chain links are outer and inner plates connected by pivot pins and means spacing the plates apart to leave gaps for the reception of the rod.

3. A dummy bar according to claim 2 in which the spacing means include at least one spacer carried by each pivot pin to form the gap between plates pivoted on it.

4. A dummy bar according to claim 3 in which the rod or each rod is restrained laterally at each pivot pin by a dowel pin inserted in a hole in a plate to extend into the gap in which the rod lies, the rod passing between the pivot pin and the dowel pin.

5. A dummy bar according to claim 2 in which the chain links are formed from pairs of outer plates alternating with single inner plates, each inner plate being received at each end between the two neighbouring outer plates with a single pivot pin passing through the three plates.

6. A dummy bar according to claim 2 in which the chain is composed of two or more pairs of outer and inner links with pivot pins common to all the links, and two rods, one on each side of each pivot pin, lie between the outer and inner links of each pair.

7. A dummy bar according to claim 2 having at least two rods, each composed of one or more lengths, the junction between individual lengths in different rods being staggered.

References. Cited by the Examiner UNITED STATES PATENTS 944,668 12/1909 Douteur 22-572 2,947,075 8/ 1960 Schneckenburger et al. 2257.2

FOREIGN PATENTS 704,512 4/1941 Germany. 728,412 4/1955 Great Britain.

1. SPENCER, OVERHOLSER, Primary Examiner, R. ANNEAR, Assistant Examiner, 

1. A DUMMY BAR FOR USE IN THE CONTINUOUS CASTING OF METAL COMPRISING A CHILL PLATE AND A LINK CHAIN INCLUDING PIVOTED LINKS, AT LEAST ONE RESILIENT ROD EXTENDING THROUGH THE RUN OF THE CHAIN, AND MEANS RESTRAINING THE ROD AGAINST LATERAL MOVEMENT ONLY AT THE PIVOT POINTS OF THE 